Major was a militaryrank, the equivalent of which was used by the service organizations of many civilizations. As a traditional grade, major was a line officer of a fighting organization, below a lieutenant colonel and above a captain. In comparison to naval ranking systems, this rank was equivalent to the naval lieutenant commander rank.

Some rank systems used the term major in conjunction with other ranks to create a different grade, such as major general.

In the episode "Patterns of Force", Captain Kirk addresses an SS officer several times as "major" even though the officer wears both the collar and shoulder insignia of a colonel. This was a common problem throughout the episode in that several characters wore rank insignia which did not correspond to the ranks spoken of in the dialogue.